How does Pro version support 4/5 button mouses?

How does Pro version support 4/5 button mouses? Does it mean you can hold down the right mouse button and click button 4 or 5 to initiate a gesture action?

Yes. You can assign actions to 4MB and 5MB, up and down. Though there are only a few special cases when it makes sense to assign different actions to both since you cannot get action assigned to up without triggering the down. I tried pressing 4MB down, then holding down RMB and releasing 4MB but it did not work and even if it did, I would get the default (I mean non-StrokeIt) action assigned to 4MB.

And one more thing. In case you have a Logitech mouse: Up does not work when SetPoint is active.

Anyway, we got two more "gestures" and that's nice.